Hub gears or internal-gear hubs are sophisticated gear systems commonly used on bicycles.

Hub gear systems generally have a long and largely maintenance-free life though some are not suitable for high-stress use in competitions or hilly, off-road conditions.

Better commuter or urban cycles such as Dutch bicycles commonly have 7-speed gear-hubs with 8-speed systems becoming increasingly available. Older or lesser cost utility bicycles often use 3-speed gear-hubs, e.g. the public bicycle rental programmes in Paris, Montreal, Lyon, London, and Washington, DC. Many folding bicycles use 3-speed gear-hubs. Hubs with up to 14 gears are available.

Gear-hubs use internal planetary or epicyclic gearing. Unlike derailleur gears, where the gears and mechanism are exposed to the elements, hub gears and lubricants are sealed within the hub-shell of the bicycle's rear wheel.

Gear changing for the hub was traditionally accomplished by a lever connected to the hub via a cable. Twist-grip style shifters are more popular today.